Preparation of trans cyclohexane,1,4-diisocyanate and related compounds

ABSTRACT

A process is disclosed for selectively making trans-cyclohexane-1,4-diisocyanate, trans-cyclohexane-1,4-diamine, a trans-cyclohexane-1,4-diurethane, a trans-cyclohexane-1,4-diurea and trans-cyclohexane-1,4-disulphonyl urea by reacting ammonia with a mixture of cis and trans cyclohexane-1,4-dicarboxylic acid, a lower alkyl ester, a glycol ester, an oligomeric ester or a polyester to make a solid trans-dicarboxylic acid diamide in a first step. The diamide is chlorinated to form trans-cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide. The latter compound is then converted into a 
     (a) trans-cyclohexane-1,4-diamine with an alkali metal hydroxide or alkaline earth metal hydroxide; or into a 
     (b) a trans-cyclohexane-1,4-diurethane by reaction with an alcohol or glycol in a reaction mixture containing an alkali metal hydroxide or alkaline earth metal hydroxide; or into 
     (c) a trans-cyclohexane-1,4-diurea by reaction with a primary or secondary amine in a reaction mixture containing an alkali metal hydroxide or alkaline earth metal hydroxide; or into a 
     (d) trans-cyclohexane-1,4-sulphonyl urea by reaction with a primary sulphonamide in a reaction mixture containing an alkali metal hydroxide and dimethyl formamide and water. The diurea prepared in (c) may be converted into trans-cyclohexane-1,4-diisocyanate with gaseous hydrogen chloride in an inert solvent. The diurethane prepared in (b) and the disulphonyl urea prepared in (d) may be thermally decomposed into trans-cyclohexane-1,4-diisocyanate.

This is a division, of application Ser. No. 215,415, filed Dec. 11,1980, U.S. Pat. No. 4,418,211, which is a Division of application Ser.No. 049,112, filed June 18, 1979, U.S. Pat. No. 4,275,223 which in turnis a Division of Ser. No. 883,949, filed Mar. 6, 1978 U.S. Pat. No.4,203,916.

This invention relates to the stereo-specific synthesis oftrans-cyclohexane-1,4-diisocyanate, trans-cyclohexane-1,4-diamine,trans-cyclohexane-1,4-diurethanes, trans-cyclohexane-1,4-diureas andtrans-cyclohexane-1,4-disulphonyl ureas.

Cyclohexane-1,4-diisocyanate, cyclohexane-1,4-diamine,cyclohexane-1,4-diurethanes, cyclohexane-1,4-disulphonyl ureas andcyclohexane-1,4-diureas are valuable starting materials for theproduction of polyurethanes, polyamides and other polymers. Importantproperties of these polymers, e.g. their mechanical strength, shrinkresistance and glass transition point, depend particularly upon thestereo isomeric form of the cyclohexane derivatives used. The higher theproportion of trans-isomers in the mixture of the isomericcyclohexane-1,4-derivatives, the more favorable are these properties.Since any of the heretofore available methods of synthesizingcyclohexane-1,4-derivatives always gives rise to a mixture of the cis-and the trans-isomers, it is desirable to increase the concentration oftrans-compound or even to obtain pure trans-isomer.

The starting point in all previous attempts was cyclohexane-1,4-diamine.This compound is one of several produced when p-phenylene diamine ishydrogenated on nickel or cobalt catalysts in methylcyclohexane or indioxane or decaline at 180° C./100 or 150 atmospheres (Hoshino, Bull.chem. Soc. Japan 19, (1944), 153, 154; J. chem. Soc. Japan 62 (1941),190, 192; C.A. 1942, 5140; U.S. Pat. No. 2,175,003). In the processdescribed in U.S. Pat. No. 3,520,928, p-phenylene diamine is used in theform of a salt of a mineral acid and hydrogenation is carried out usingan acid resistant catalyst, e.g. a platinum or palladium catalyst inaqueous solution at a temperature of from 50° to 150° C. and atpressures of from 0.35 to 14 atmospheres. Ruthenium catalysts are alsosuitable for the hydrogenation of p-phenylene diamine (ChemicalAbstracts Vol. 63 (1965), 11415 h; Vol. 69 (1968), 25775 and Vol. 72(1970), 132 192k). Alkali-modified ruthenium carrier catalysts are usedin the process according to U.S. Pat. No. 3,636,108 (see also CanadianPat. No. 839,281 and Canadian Pat. No. 892,636) and a catalyst obtainedby precipitation of an oxide hydrate of ruthenium is used in the processdescribed in German Offenlegungsschrift No. 2,132,547. The diamino,1,4-diamino cyclohexane is obtained when 4-nitro aniline is hydrogenatedin the presence of colloidal platinum in acetic acid and hydrochloricacid at a temperature of 65° C. (Skita, Borendt, Ber. 52, 1534) or inthe presence of a ruthenium catalyst at 20° to 250° C. and a pressureabove 7 atmospheres (U.S. Pat. No. 2,606,925). In all of theseprocesses, a mixture of the cis- and the trans-forms is obtained, inwhich the equilibrium is established at approximately 70% of thetrans-form and 30% of the cis-form (Chem. Abstracts 82 (1975), 111479a).

Trans-cyclohexane-1,4-diamine can be obtained from this isomeric mixtureby fractional crystallization as described in U.S. Pat. No. 3,657,345,but several crystallizations are required to achieve this. Moreefficient separation of the isomers is possible by fractionalcrystallization of suitable derivatives. One example of this is thefractional crystallization of bis-methyl carbamates followed byhydrolysis with hydrogen chloride (Chem. Abstr. 74 (1971), 87370c). Onedisadvantage of this method is that it requires an additional step forthe preparation of the derivative and another for regenerating thediamine.

In U.S. Pat. No. 3,491,149 a process is described in which the isomericmixture is reacted with an organic polyhydroxyl compound having from 2to 13 carbon atoms and 2 to 4 hydroxyl groups, optionally in thepresence of a solvent such as cyclohexane dimethanol, to produce a"polyolate" coordination compound. The cis- and trans-isomers of thiscoordination compound differ more widely from each other in theircrystallization behavior than the corresponding 1,4-diamino cyclohexaneisomers and can therefore be separated from each other more easily. Thetrans-coordination compound is subsequently subjected to fractional orazeotropic distillation at atmospheric or reduced pressure so thattrans-1,4-diamino cyclohexane and the polyhydroxyl compound are againseparated from each other. Alternatively, however, this process can becarried out with only a single crystallization step, in which case onlypart of the original trans-isomer is recovered. The filtrate thencontains the remainder of the trans-isomer and virtually all of theoriginal cis-isomer.

Such mixtures of stereo isomers of 1,4-diamino cyclohexane which containmore cis-isomer than corresponds to the equilibrium concentration may beworked up by a process described in U.S. Pat. No. 3,657,345. In thisprocess, the reaction mixture is treated with hydrogen under pressure at150° to 300° C. in the presence of an alkali-modified ruthenium catalystand in the presence of ammonia. The usual equilibrium of about 70%trans-isomer and about 30% cis-isomer is re-established and part of thetrans-isomer may again be separated from the cis-isomer by fractionalcrystallization. The process may also be carried out with the additionof p-phenylene diamine.

The trans-isomer can also be obtained in a comparatively pure form byconverting a pure precursor of the trans-isomer into trans-1,4-diaminocyclohexane. The following are examples: reaction of finely dividedtrans-hexahydroterephthalic acid diazide with water followed bytreatment with water under pressure at 120° C. and heating of thereaction product to 140° C. with concentrated hydrochloric acid underpressure (Curtius, J. prakt. Chem. (2) 91, 33); heating oftrans-hexahydro-p-phenylene diurethane with concentrated hydrochloricacid in a tube reactor (Curtius, J. prakt. Chem. (2) 91, 34);hydrogenation of trans-1,4-dinitro-cyclohexane in acetic acid and in thepresence of a platinum catalyst at 25° C. (A. T. Nielsen, J. Org. Chem.Vol. 27 (1962), 1,998-2,001). In these processes, however, the problemof preparing a stereo specific isomer is simply shifted to the chemicalprecursor stage of the isomer.

Pure trans-cyclohexane-1,4-diamine obtainable by the methods describedabove may subsequently be converted intotrans-cyclohexane-1,4-diisocyanate by phosgenation in known manner, andthis diisocyanate may in turn be converted into puretrans-cyclohexane-1,4-diurethanes or -diureas. Summarizing, it has beenfound that none of the processes mentioned above is a stereo specificsynthesis of the cyclohexane-1,4-derivatives but that they require theseparation of a mixture of cis- and trans-isomers ofcyclohexane-1,4-diamine or of a precursor thereof and secondaryreactions of the separated trans-isomer.

Theoretically, Hofmann's degradation of cyclohexane-1,4-dicarboxylicacid diamide is available for the preparation ofcyclohexane-1,4-diamine. As is well known, Hofmann's degradation ofcarboxylic acid amides leads to the amine via the stages of theN-chloramide and the isocyanate. If the reaction is carried out in thepresence of sodium alcoholate in an alcohol, a urethane is obtained; ifthe reaction is carried out in the presence of a primary or secondaryamine, a substituted urea is obtained; if the reaction is carried out inthe presence of a primary sulphonamide in a mixture of dimethylformamideand water, a substituted sulphonyl urea is obtained. The N-chloramide,and hence the isocyanate, can only rarely be isolated as intermediateproducts of Hofmann's degradation. It is therefore generally necessaryto synthesize the isocyanate from the substituted urea, a urethane or asulphonyl urea or by some other means. Hofmann's degradation ofcyclohexane-1,4-dicarboxylic acid diamide also leads directly tocyclohexane-1,4-diamine; the intermediate stages cannot be isolated. Thecyclohexane-1,4-dicarboxylic acid diamide required for this process caneasily be obtained in an analytically pure form, either by the processdescribed in German Pat. No. 2,410,537, which consists of reactingcyclohexane-1,4-dicarboxylic acid with urea in oleum having aconcentration of at least 10% by weight or in chlorosulphonic acid, andwhich gives a yield of 82%, or by the process disclosed in GermanOffenlegungsschrift No. 2,437,470, which consists of ammonolysis of anoligoester or polyester of cyclohexane-1,4-dicarboxylic acid, and whichprovides a yield of 97%. If a product obtained by one of these processesor by any of the other known processes, for example from the ammoniumsalt of carboxylic acid or by the reaction of the anhydride, the acidchloride or an ester of cyclohexane-1,4-dicarboxylic acid is subjectedto Hofmann's degradation, the product obtained is invariably a mixtureof the cis-and trans-isomers. This is also true whencyclohexane-1,4-dicarboxylic acid-bis-N-chloramide obtained by thechlorination of cyclohexane-1,4-dicarboxylic acid diamide according tothe process described in German Offenlegungsschrift No. 2,502,412 issubjected to Hofmann's degradation. In other words, it has hitherto beenimpossible to prepare any of the above mentioned pure trans-isomers bymeans of Hofmann's degradation.

It is therefore an object of this invention to provide a process forselectively making trans-cyclohexane-1,4-diisocyanate,trans-cyclohexane-1,4-diamine, trans-cyclohexane-1,4-diurethane,trans-cyclohexane-1,4-diurea, and trans-cyclohexane-1,4-sulphonyl ureawhich does not require separation of the trans- and cis-isomers.

Another object of the invention is to provide a process forpreferentially making one of the said trans-compounds from a mixture ofcis- and trans-isomers of the starting compound.

It has now surprisingly been found that with suitable choice of thereaction parameters it is possible to provide a method of synthesis bywhich the desired trans-isomer can be obtained stereo-specifically andin high yields from a cis/trans mixture of cyclohexane-1,4-dicarboxylicacid or one of its monomeric, oligomeric or polymeric esters.

The present invention therefore provides a process for the preparationof trans-cyclohexane-1,4-diisocyanate, trans-cyclohexane-1,4-diamine,trans-cyclohexane-1,4-diurethanes, trans-cyclohexane-1,4-diureas ortrans-cyclohexane-1,4-disulphonyl-ureas which is characterized in thatcyclohexane-1,4-dicarboxylic acid, a lower alkyl ester, a glycol ester,an oligomeric ester or a polyester thereof or a mixture of the aforesaidcompounds is used as starting material, the said acid or ester (oresters) is treated with ammonia in a polyhydric alcohol such as ethyleneglycol at a temperature of from about 25° to about 200° C. and under anammonia partial pressure of 0.1 to 50 bar, and the solid dicarboxylicacid diamide which separates under these conditions is freed from watersoluble constituents adhering to it and is suspended in aqueous mineralacid or in water and chlorinated at temperatures of from 0° to 40° C.,and the cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide therebyobtained is washed free from chlorine with cold water and finally

(a) is converted into trans-cyclohexane-1,4-diamine by treatment with analkali metal or alkaline earth metal hydroxide,

(b) is converted into a trans-cyclohexane-1,4-diurethane by reactionwith an alcohol or with a glycol in a reaction mixture containing analkali metal hydroxide or alkaline earth metal hydroxide or analcoholate,

(c) is converted into a trans-cyclohexane-1,4-diurea by reaction with aprimary or secondary amine in the presence of an alkali metal oralkaline earth metal hydroxide or

(d) is converted into a trans-cyclohexane-1,4-sulphonyl urea bytreatment with a primary sulphonamide in the presence of an alkali metalhydroxide in a mixture of dimethyl formamide and water or the diureaobtained according to (c) is converted intotrans-cyclohexane-1,4-diisocyanate by treatment with gaseous hydrogenchloride in an inert solvent or the urethane obtained according to (b)is converted into trans-cyclohexane-1,4-diisocyanate by thermaldecomposition in the gaseous phase or in the liquid phase, optionally inan inert solvent or the disulphonyl urea obtained according to (d) isconverted into trans-cyclohexane-1,4-diisocyanate by heat treatment inan inert solvent.

In the process provided by the present invention, the ratio of cis- totrans-isomer in the starting material is unimportant since the desiredreaction products are obtained substantially exclusively in thetrans-form even if the starting materials have a very high cis/transratio, for example of 10:1. It is known that in compounds which exist inthe stereo isomeric form, an equilibrium between the cis-form and thetrans-form is invariably established under strongly alkaline conditionsand at high temperatures. It is therefore surprising that the processaccording to the invention, in which strongly alkaline conditions andhigh reaction temperatures are employed in at least two reaction stages,nevertheless results almost exclusively in trans-compounds, which meansthat in the present case the establishment of a cis/trans equilibriumunexpectedly does not take place.

One important feature of the process provided by the invention is thatit cannot be carried out with any cyclohexane-1,4-dicarboxylic aciddiamide prepared by just any available method. On the contrary, thecyclohexane-1,4-dicarboxylic acid diamide used as the starting materialmust be one which has been prepared by ammonolysis of a lower alkyl orglycol ester or of an oligomeric or polymeric ester of cyclohexane1,4-dicarboxylic acid in a polyhydric alcohol or by amidation ofcyclohexane-1,4-dicarboxylic acid in the presence of a polyhydricalcohol, and only the water insoluble constituents may be used for thesubsequent reaction.

A process for the preparation of cyclohexane-1,4-dicarboxylic aciddiamide from oligomeric or polymeric esters ofcyclohexane-1,4-dicarboxylic acid is disclosed in German Pat. No.2,437,470. Examples of polyhydric alcohols from which the required oligoesters or polyesters may be obtained include ethylene glycol, diethyleneglycol, 1,3-propane diol, 1,4-butane diol, 1,6-hexane diol 1,8-octanediol, 1,10-decane diol, 1,2-propane diol, 2,2-dimethyl-1-1,3-propanediol, 2,2,4-trimethyl hexane diol, cyclohexane-1,4-dimethanol, glyceroland the like. Copolycondensates of cyclohexane-1,4-dicarboxylic acidwith several of the above mentioned diols may also be used as startingmaterials. The polyhydric alcohols already mentioned above as estercomponents, or mixtures of these alcohols, may be used as the reactionmedium. It is preferred to use, as the reaction medium, that alcoholwhich forms the alcohol component of the cyclohexane-1,4-oligoester or-polyester. According to a preferred embodiment of the invention, anoligomeric or polymeric ethylene glycol ester ofcyclohexane-1,4-dicarboxylic acid is used as the starting material, andammonolysis is carried out in ethylene glycol. Moreover, instead ofusing a previously prepared oligoester or polyester, the reactionmixture obtained from its preparation, which contains excess diol, maybe used. The quantities of polyhydric alcohol used as reaction mediumare in the region of 100% to 1,000% by weight, based on the quantity ofoligoester or polyester used.

The reaction temperatures may be within the range of from 25° to 200° C.and are preferably from about 50° to about 160° C. The ammonia partialpressures are in the region of 0.1 to 50 bar. For practical and economicreasons, ammonolysis is preferably carried out at ammonia partialpressures below 20 bar. The reaction time required depends on theoligoester or polyester put into the process, the ammonia partialpressure and the reaction temperature and, where ammonolysis is carriedout on an oligoester or polyester suspension, it also depends decisivelyon the thickness of the starting material. If ammonolysis is carried outin solution or on a very finely divided material, it is generallycompleted in less than two hours under the preferred conditions of theprocess. Longer reaction times are required for a material consisting ofvery coarse particles, for example from five to six hours in the case ofa polyester with a particle size of 5 mm.

Ammonolysis may be carried out, for example, by first dissolving orsuspending the oligoester or polyester in the polyhydric alcohol andthen passing gaseous ammonia through the solution or suspension underthe reaction conditions, at the same time thoroughly mixing thecomponents. The solution or suspension may also be introduced into anautoclave into which the required quantity of ammonia is introduced intogas space while the contents of the autoclave are vigorously mixed.

When a very coarse polymer material is used, it is advisable first todissolve it in the polyhydric alcohol at a temperature above theintended reaction temperature and then to cool the solution to thereaction temperature. Under these conditions, the polyester precipitatesin a finely divided form if it does not remain completely in solution,and thus becomes more readily accessible to the action of ammonia. Inthis way, short reaction times can be achieved for even a coarsestarting material.

The diamide may be prepared from a glycol ester by the process describedin U.S. Pat. No. 3,296,303. According to the process described in thisU.S. patent, ammonolysis is carried out on an ester of ethylene glycol,propylene glycol or diethylene glycol at a temperature of from 25° C. to130° C. in excess glycol, but the process is not restricted to thestarting compounds and temperature conditions mentioned in the Patent.Other suitable glycol esters are those mentioned above as startingcompounds for the preparation of oligomeric and polymeric esters.

Lower alkyl esters may be converted similarly intocyclohexane-1,4-dicarboxylic acid diamide. Suitable lower alkyl estersinclude in particular compounds having from 1 to 4 carbon atoms in thealkyl group, for example methyl, ethyl, propyl, butyl, and isobutylesters of cyclohexane-1,4-dicarboxylic acid. It is advantageous totrans-esterify the alkyl ester in a polyhydric alcohol, preferably inethylene glycol, and to remove the resulting lower alcohol from thereaction mixture by distillation. This process may be carried out byheating the alkyl ester in the polyhydric alcohol at a temperature offrom 50° C. to 120° C. while passing a slow stream of ammonia throughthe reaction mixture. It is surprisingly found that trans-esterificationis so greatly accelerated by gaseous ammonia that the usualtrans-esterification catalyst can be dispensed with. Subsequentammonolysis of the glycol ester results in a purer diamide and higheryields than ammonolysis of the alkyl ester because the lower alcoholswhich are split off during ammonlysis form by-products with ammonia,e.g. primary amines.

Ammonolysis of polymeric, oligomeric and monomeric diesters ofcyclohexane-1,4-dicarboxylic acid may be carried out, by the processdescribed in German Pat. No. 2,437,470, at temperatures of from 25° C.to 200° C., preferably at 50° C. to 160° C., and at an ammonia partialpressure of from 0.1 to 50 bar, preferably at 1 to 20 bar.

Cis/trans-cyclohexane-1,4-dicarboxylic acid may also be converted intocyclohexane-1,4-dicarboxylic acid diamide by reaction with ammonia in apolyhydric alcohol. This reaction is suitably carried out by esterifyingthe cis/trans mixture of cyclohexane-1,4-dicarboxylic acid with apolyhydric alcohol, preferably ethylene glycol, and then introducingammonia into the reaction mixture under the above mentioned conditionsof ammonolysis at 50° C. to 160° C. and an ammonia partial pressure offrom 0.1 to 50 bar. The yield of cyclohexane-1,4-dicarboxylic aciddiamide obtained in this process is about 84% of the theoretical yield.

Essential to the process according to the invention is not only theparticular method of synthesis to be used for the requiredcyclohexane-1,4-dicarboxylic acid diamide but also the feature that onlythat portion of the dicarboxylic acid diamide which is obtained as solidfrom the reaction mixture of the special process of preparation may beused as starting compound for the subsequent stages of synthesis, andonly after it has been freed from the water-soluble constituentsadhering to it. In the course of the preparation of thecyclohexane-1,4-diamide in a polyhydric alcohol, a substantialproportion of the diamide is left dissolved in the reaction mixture.When ethylene glycol is used as the reaction medium, only about 80% ofthe diamide, which is formed in virtually quantitative yield, is finelyobtained. The diamide which remains dissolved in the filtrate of thereaction mixture after removal of the solid diamide is not suitable forthe synthesis of the pure trans-compound to be obtained according to theinvention. The same applies to the water-soluble or methanol-solublediamide constituents which adhere to the solid precipitated diamide.They must be removed by washing, for example with water. However, theproportions of diamide which are dissolved in the reaction mixture arenot lost. The glycollic mother liquor may be used again for ammonolysis,in other words it may be recycled. In that case, it is even found thatthe proportion of cyclohexane-1,4-dicarboxylic acid diamide precipitatedfrom the reaction mixture is increased to over 95% of the theoreticalyield. The mother liquor left after removal of the solid precipitateddicarboxylic acid diamide is therefore kept in circulation in theprocess according to the invention, i.e. it is re-used for the reactionof the cyclohexane-1,4-dicarboxylic acid or its esters. The watersoluble diamide fraction contained in the wash waters of theprecipitated solid diamide may also be used again for ammonolysis. Thewash waters may be collected, concentrated by evaporation, combined withthe glycollic mother liquor and then freed from water and any adheringlower alcohols by distillation.

Cyclohexane-1,4-dicarboxylic acid diamido obtained by the processdescribed above is then suspended in an aqueous mineral acid by theprocess according to German Offenlegungsschrift No. 2,502,412 orchlorinated in water at 0° to 40° C. to formcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide.

Any suitable aqueous mineral acid may be used such as, for example,dilute aqueous hydrochloric acid, sulphuric acid or phosphoric acid. Itis preferred to start with a neutral aqueous suspension of the diamideso that the hydrogen chloride formed as by-product of chlorinationdissolves in the reaction mixture and the reaction therefore takes placein a dilute aqueous hydrochloric acid medium. Moreover, it is preferredto start with a dilute hydrochloric acid or dilute sulphuric acidaqueous suspension of the diamide.

Chlorination of the diamide is exothermic. It may be carried out at atemperature of from 0° C. to 40° C. Higher temperatures are adisadvantage in that they cause the formation of substantial quantitiesof cyclohexane-1,4-dicarboxylic acid due to hydrolysis. For economicreasons, chlorination is preferably carried out at 5° C. to 25° C., andthe heat of reaction may be removed by cooling with water.

Chlorination may be carried out either at atmospheric pressure or at anelevated pressure. Although the reaction time required decreases withincreasing pressure, the preferred pressure range is approximatelybetween 1 and 6 bar for economic reasons.

Since chlorination takes place in a heterogeneous phase, thorough mixingof the suspension is required. The reaction mixture should at least bediluted sufficiently to allow it to be easily stirred or mixed in someother way. The preferred dilution of the reaction mixture is about 100to 200 g of diamide per liter of water or aqueous mineral acid.

When the above reaction conditions are observed, chlorination iscompleted after about 0.25 to 2 hours. The diamide is convertedvirtually quantitatively into the bis-N-chloramide without any solutiontaking place in the meantime. The only solid contained in the suspensionafter chlorination has been completed is cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide, which can be separated easily from the liquidphase e.g. by filtration or centrifuging. Water at 0° C. to 15° C. isused for washing, preferably ice water. The precipitate should be washedfree from chlorine because the presence of free chlorine acting asoxidizing agent interferes with the subsequent Hofmann reaction. Theproduct is obtained maximally pure after washing followed by drying,e.g. at 50° C. under vacuum. For the subsequent stages of the reaction,only the insoluble portions of cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide which have been washed free from chlorine withcold water are used.

The cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide which has beenobtained as described above by ammonolysis of a monomeric, oligomeric orpolymeric ester of cyclohexane-1,4-dicarboxylic acid in a polyhydricalcohol or by amidation of cyclohexane-1,4-dicarboxylic acid in apolyhydric alcohol followed by chlorination of the resultingcyclohexane-1,4-dicarboxylic acid diamide may be subsequently convertedinto a diamine, a diisocyanate, a diurethane, a diurea or adisulphonylurea.

Synthesis of the trans-cyclohexane-1,4-diamine is carried out byreaction of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide with analkali metal or alkaline earth metal hydroxide. This is carried out bydissolving or suspending the bis-N-chloramide in a hydroxide, preferblyan aqueous hydroxide, and heating. Any alkali metal or alkaline earthmetal hydroxide may be used but sodium hydroxide and calcium hydroxideare preferred to the other hydroxides such as potassium hydroxide,barium hydroxide, magnesium hydroxide and the like for economic reasons.The hydroxide is preferably used in a stochiometric quantity. It isneither necessary nor of advantage to use an excess of hydroxide.

The reaction of the bis-N-chloramide is preferably carried out at atemperature within the range of from about 20° C. to about 95° C.,preferably from about 30° C. to 80° C. Solutions or suspensions ofbis-N-chloramide at concentrations of from 5% to 45% by weight arepreferably used.

The diamine may be isolated from the reaction mixture by extraction withchloroform, 1,2-dichloroethane or some other solvent. However, thediamine precipitates in such purity from the reaction mixture that itmay also be separated by fractional crystallization. Separation by steamdistillation or precipitation of the amine as a salt with sulphuric acidor hydrochloric acid are other possible methods of separation.

The rearrangement reaction is highly exothermic and is preferablycarried out adiabatically. If an adiabatic method is impossible due toexcessive evolution of heat, as may happen if high initialconcentrations of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide areemployed, the reaction may be carried out under conditions of vaporcooling, for example using methylene chloride as vaporizing agent.

To pressure trans-cyclohexane-1,4-diurethanes,cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide is reacted with ahydroxyl compound in the presence of an alkali metal or alkaline earthmetal hydroxide. The hydroxyl compounds used may be any alcohol orphenol which is capable of at least partly dissolving an alkali metal oralkaline earth metal hydroxide. Such hydroxyl compounds includemonohydric alcohols, in particular the lower alkyl alcohols such asmethyl, ethyl, propyl, isopropyl, butyl and isobutyl alcohol as well asglycols, e.g. ethylene glycol, propylene glycol and glycerol, and manycarbocyclic and heterocyclic phenols.

The following are examples of suitable carbocyclic phenols: monovalentmonocyclic phenols such as phenol itself, o-, m- and p-cresol, thexylenols, thymol and carvacrol, divalent and higher valent monocyclicphenols, e.g. pyrocatechol, resorcinol, hydroquinone, pyrogallol,hydroxyhydroquinone, phloroglucinol, other monocyclic polyhydroxybenzenes and dicyclic and polycyclic phenols such as naphthols andhydroxyanthracenes. Substitution products of the above mentioned phenolsare also suitable, e.g. the corresponding halogenated, sulphonated andnitrated compounds and the corresponding ether derivatives. Examples ofheterocyclic phenols include the hydroxy derivatives of heterocyclone,pyrrole, furan, thiophene, pyrazole, imidazole, oxazole, thiazole,triazole, tetrazole, pyridine, pyrimidine, pyrazine and triazine and thecorresponding benzo-condensed derivatives.

In the synthesis of trans-diurethanes, two mol of alkali metal hydroxideor one mol of alkaline earth metal hydroxide are required for each molof bis-N-chloramide. Stoichiometric quantities of hydroxide arepreferably used in practice. If excess quantities of hydroxide are used,trans-cyclohexane-1,4-diamine is formed as by-product whereas, when lessthan equivalent quantities of hydroxide are used, the reaction does notproceed quantitatively and substantial quantities of acyl ureas areformed, among other by-products.

The process is carried out at temperatures of from 0° C. to 150° C.,preferably 10° C. to 80° C. Diurethane formation proceeds exothermally.

The hydroxy compound is used in excess and may also serve as reactionmedium. The minimum quantity required is that which will keep themixture stirrable. It is therefore preferred to use saturated alkalimetal hydroxide or alkaline earth metal hydroxide solutions in thealcohol or phenol used.

The process is preferably carried out by first preparing a solution ofthe hydroxide in the alcohol or phenol and then introducing thecyclohexane-1,4-dicarboxylic acid-bis-N-chloramide with stirring andcooling to temperatures below 10° C. The bis-N-chloramide generallydissolves within a few minutes with salt formation. A clear colorlesssolution is formed, from which a fine, white bulky precipitate separatesgradually, more rapidly if the reaction mixture is heated totemperatures above 25° C. If desired, the reaction may be carried out ina suspension of the alkali metal or alkaline earth metal salt ofcyclohexane-1,4-carboxylic acid-bis-N-chloramide. In that case, the saltdissolves during the reaction at the rate at which the diurethane formsand precipitates. Here again, the reaction is highly selective althoughat no point is a clear reaction solution obtained. The precipitatecontains alkali metal chloride or alkaline earth metal chloride in thetrans-diurethane. The reaction mixture may be worked up by, for example,the following method: In the case of trans-diurethanes which aredifficult to dissolve in water, the precipitate is filtered off and thefiltrate is concentrated by evaporation. The precipitate therebyobtained also consists of alkali metal or alkaline earth metal chlorideand trans-diurethane. The precipitates are combined and digested with asmall quantity of water, whereby the alkali metal chloride or alkalineearth metal chloride is dissolved away. In the case of trans-diurethaneswhich are less difficult to dissolve in water, the reaction mixture isevaporated to dryness and extracted with an organic solvent such asethanol, ethyl acetate or chloroform, the alkali metal or alkaline earthmetal chloride being left behind as residue. The liquid phase whichcontains the trans-diurethane, is then dried.

The trans-diurethanes mentioned above may be obtained highly pure and inalmost quantitative yields by the process described here.

Preparation of the trans-diureas is carried out according to theinvention by reacting the cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide which has been obtained as described above with anamine in an aqueous medium in the presence of an alkali metal oralkaline earth metal hydroxide or alkali metal or alkaline earth metaloxide. The amines used may be primary or secondary, aliphatic oraromatic, mono-functional or poly-functional amines. Examples of suchamines include ammonia, methylamine, dimethylamine, ethylamine,diethylamine, ethylenediamine, isobutylamine, tertiary butylamine,aniline, ethanolamine, the isomeric cyclohexylamines, the isomericphenylenediamines and substituted derivatives thereof, e.g.,N-N'-diisopropylphenylenediamine and heterocyclic amines such asmorpholine.

The reaction is carried out in water. The amine is used in excess,preferably in an excess of about 60 mol %. The reaction is carried outat temperatures of from 10° to 100° C., preferably at 25° to 70° C. Thereaction time is generally from 2 to 5 hours.

The process is suitably carried out by suspendingcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide in water withvigorous stirring and adding the stoichiometric quantity of aqueoushydroxide dropwise at temperatures of from 0° to 5° C. with cooling. Aclear solution of the alkali metal or alkaline earth metal salt ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide is thereby obtained.The amine is then added portion-wise and the reaction mixture isthereafter heated to a temperature of from 25° C. to 75° C. and kept atthis temperature until the end of the reaction. After cooling, theprecipitate of trans-diurea is filtered off, washed and dried. A secondfraction of the trans-diurea may be recovered from the filtrate by firstneutralizing the filtrate with a mineral acid, removing water, and thenextracting with a suitable organic solvent, e.g. acetone or ethylacetate.

The process disclosed in German Pat. No. 2,502,428 may be used toprepare trans-cyclohexane-1,4-disulphonyl-ureas. According to thisprocess, cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide is reactedwith a sulphonic acid amide of the general formula R--SO₂ --NH₂, inwhich R represents an amino group, a straight or branched chain,saturated or unsaturated aliphatic group having from 1 to 20 carbonatoms, a cycloaliphatic group having from 4 to 10 carbon atoms, asubstituted or unsubstituted aromatic group or an alkyl aromatic orheterocyclic group, in a mixture of dimethyl formamide and water in thepresence of excess alkali metal hydroxide at a temperature of from 10°C. to 50° C. Any primary sulphonamide may be used, both inoganic primarysulphonamides, e.g. sulphamide, and organic primary sulphonamides, forexample aliphatic, cycloaliphatic and aromatic sulphonamides, and thesemay also be substituted. Suitable substituents are those which are inerttowards isocyanates or react more slowly than sulphonamides, thus alkyl,nitro, halogen, sulpho, alkoxy, nitrilo, phosphonato, sulphamido andphenyl substituents are suitable. The following are examples of suchorganic sulphonamides: methane sulphonamide and its homologuescontaining from 2 to 20 carbon atoms, benzene sulphonamide, p-toluenesulphonamide, p-fluorobenzene sulphonamide, p-chlorobenzenesulphonamide, p-bromobenzene sulphonamide, p-iodobenzene sulphonamide,2,4,5-trichlorobenzene sulphonamide,3-sulphamidobenzene sulphoamide,2-naphthyl sulphonamide and cyclohexyl sulphonamide.

The composition of the reaction medium to be employed depends on thesolubility of the alkali metal hydroxide in the dimethyl formamide/watermixture, the solubility of the sulphonamide salt in dimethyl formamideand the basicity of the sulphonamide. The quantity of water should besufficient to allow the alkali metal hydroxide to dissolve as far aspossible completely in the reaction medium but, at the same time, itmust not exceed a certain limit, beyond which the reaction does not stopat the formation of sulphonyl urea but proceeds to the acyl urea. Thislimit, which is specific to each sulphonamide, depends on the basicityof the sulphonamide and on its solubility. The quantity of dimethylformamide should be sufficient to allow the sulphonamide salt todissolve at least partly in the reaction medium. Suitable proportionscan easily be determined by simple preliminary tests. Satisfactoryresults are achieved with a dimethyl formamide/water ratio of from 5:1to 14:1.

For economic reasons, the alkali metal hydroxide used is preferablysodium hydroxide although the other alkali metal hydroxides are equallysuitable. The alkali metal hydroxide should be used in at least thestoichiometric quantity. Four mol of alkali metal hydroxide are requiredfor each mol of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramidebecause it is only in its anionic form that the sulphonamide reacts asalkali metal salt in the required manner. In many cases it has beenfound advantageous to use an excess of alkali metal hydroxide. It ispreferred to use an excess of up to 2 mol of alkali metal hydroxide permol of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide.

Cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide and the sulphonamidemay be included in the process in stoichiometric quantities, i.e. in amolar ratio of 1:2, but the sulphonamide, which is generally the lessexpensive reactant, may suitably be added in an excess of up to 2 mol.

According to the invention, the trans-diureas prepared as describedabove may be converted into trans-cyclohexane-1,4-diisocyanate bytreatment with gaseous hydrogen chloride in a solvent. Any of the abovementioned trans-diureas which have been prepared from a secondary aminemay be used as starting materials. The reaction temperature employed ispreferably within the range of from 80° C. to 200° C., more preferably100° C. to 160° C. Gaseous hydrogen chloride is used either in thestoichiometric quantity or in excess. It may also be mixed with an inertgas such as carbon dioxide or nitrogen. The reaction times depend on thenature of the trans-diurea and are generally in the region of from 5 to45 minutes. The nature of the solvent has no decisive influence on thecourse of the reaction. Suitable solvents include aromatic compoundssuch as benzene and toluene and chlorinated aromatic compounds such asmonochlorobenzene, 1,2-dichlorobenzene and chloronaphthalene. Theboiling point of the solvent should be higher than the reactiontemperature employed in order that the reaction may be carried out atnormal pressure, but excess pressure may be employed if desired.

Conversion of the trans-diurea may be carried out, for example, bydissolving or suspending it in a solvent, heating the resulting solutionor suspension under reflux and then passing a stream of hydrogenchloride through it, optionally diluted with an inert gas.

After complete conversion of the trans-diurea, the supply of hydrogenchloride is stopped and any hydrogen chloride left in the reactionmixture is carefully driven off by means of an inert gas. The reactionmixture is then cooled, whereby the amine hydrochloride is in most casesprecipitated quantitatively.

The method employed for working up the reaction mixture depends on thesolubility of the amine hydrochloride formed as by-product. If this isprecipitated almost quantitatively from the cooled reaction mixture, itis removed by filtration or centrifuging. The solvent is then evaporatedoff and the residue, containing trans-cyclohexane-1,4-diisocyanate, issubjected to fractional distillation. If the amine hydrochloride ispartly soluble in the cooled reaction mixture, the solvent is firstdistilled off and the diisocyanate is then separated by solventextraction with an alkane and finally subjected to fractionaldistillation. The amine can be recovered quantitatively from an aqueoussolution by reaction of the hydrochloride with an alkali metal hydroxidefollowed by extraction, and may then be used again for the preparationof the trans-diurea.

Another possible method of preparing trans-cyclohexane-1,4-diisocyanatecomprises thermal decomposition of thetrans-cyclo-hexane-1,4-diurethanes obtained by the process according tothe invention. Suitable methods are disclosed in GermanOffenlegungsschrift No. 2,410,505, British Pat. No. 1,247,451 and U.S.Pat. No. 3,962,302. In the process described in GermanOffenlegungsschrift No. 2,410,505, the urethane is introduced into anon-catalytic zone of pyrolysis which is maintained at a reactiontemperature of from 350° C. to 550° C. and a pressure of less than 1bar, the reaction products are removed from the reaction zone in thevapor phase after a dwell time therein of less than about 15 seconds,and the reaction products which are in the vapor phase are cooled tocondense cyclo-hexane-1,4-diisocyanate, the alcohol formed as by-productbeing left in the vapor phase. In the process described in British Pat.No. 1,247,451, the diurethane is heated to a temperature of from 400° C.to 600° C. in the presence of from 0.5% to 3% by weight of a Lewis acid,e.g., iron chloride or aluminum chloride, and the vapor mixture is thencondensed to separate the diisocyanate. In the process according to U.S.Pat. No. 3,962,302, thermal decomposition of the urethane is carried outin an organic solvent, e.g., an aliphatic, cycloaliphatic or aromatichydrocarbon, at 175° to 350° C.

Trans-cyclohexano-1,4-diisocyanate may also be prepared by degradationof the corresponding disulphonyl ureas. See, in this connection, theprocess by H. Ulrich et al., Angew. Chem. 78 (1966), pages 746 to 747.For example, the reaction may be carried out at temperatures of from100° to 230° C. in an inert high boiling solvent such as nitrobenzene,ortho-dichlorobenzene, 1,2,4-trichlorobenzene or 2-chloronaphthalene.

The process according to the invention provides a stereo-specificsynthesis which, starting from a cis-trans mixture ofcyclohexane-1,4-dicarboxylic acid or one of its monomeric, oligomeric orpolymeric esters, leads to numerous pure trans compounds in almostquantitative yield via the stage of a special modification of thecyclohexane-1,4-dicarboxylic acid diamide and a special modification ofthe cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide by a Hofmannrearrangement.

The process is superior to the known processes for the production ofsuch compounds in that it uses inexpensive starting materials, i.e.,cyclohexane-1,4-dicarboxylic acid or its esters, which in part areavailable as raw materials or waste products or polyester production,and leads to the desired trans compound in high yields by simple, smoothreactions which require simple apparatus. The main advantage of theprocess according to the invention is that it is based on astereo-specific synthesis. Whereas, in the known processes, the transcomponent can only be separated from the original cis-trans isomericmixture of the starting materials and worked up, the process provided bythe present invention for the first time provides for completeconversion of the cis-trans mixture of the starting materials into thedesired pure trans-reaction products, regardless of the proportion ofcis-compound to trans-compound in the starting materials.

The products obtainable by the process according to the invention arevaluable intermediate compounds. Trans-cyclohexane-1,4-diamine, forexample, may be reacted with dicarboxylic acid chlorides to producepolyamides which are distinctly superior in their physical propertiessuch as tear resistance, shrink resistance, non-fusibility and other useproperties to those products which have been produced from a cis-transisomeric mixture of cyclohexane-1,4-diamine. The reaction oftrans-cyclohexane-1,4-diamine with terephthaloyl chloride, for example,results in a polyamide which can be spun from an anisotropic solution inconcentrated sulphuric acid to produce fibers with high temperatureresistance and high modulus. Polyurethanes obtained fromtrans-cyclohexane-1,4-diisocyanate are distinguished by high elongationon tearing, high tension characteristics, low permanent elongation, highrestoring forces and absence of hysteresis losses. The properties ofpolymers produced from the pure trans-starting materials are in allcases more valuable than the properties of polymers produced from thecorresponding mixtures of cis- and trans-isomers.

The trans-cyclohexane-1,4-diisocyanate may be used for makingplyurethane elastomers, coatings and the like. The coatings haveimproved light stability over coatings prepared from arylenediisocyanates. The process provided by the invention is described inmore detail in the Examples given below. All the compounds wereidentified by their IR, NMR, UV and mass spectra. Any diureas,diurethanes or disulphonyl ureas which have not yet been described inthe literature were also prepared by addition reactions withtrans-cyclohexane-1,4-diisocyanate and their identity was confirmed bycomparisons.

Examples 1 to 5 relate to the preparation ofcyclohexane-1,4-dicarboxylic acid diamide by ammonolysis of an alkylester and glycol ester and of an oligomeric ester ofcyclohexane-1,4-dicarboxylic acid.

EXAMPLE 1

In a 1 liter glass autoclave equipped with glass inlet tube, stirrer andreflux condenser, 163.7 g (0.8185 mol) of cyclohexane-1,4-dicarboxylicacid dimethyl ester (cis/trans ratio=9:1) were added rapidly to 564 g ofethylene glycol (solvent and reactant) (˜9.1 mol) and the reactionmixture was then saturated with ammonia at room temperature. The mixturewas then slowly heated. The methanol formed in the reaction began todistill off at 80° C. When the temperature was raised to between 100° C.and 130° C. with the simultaneous introduction of ammonia, transesterification was completed and the methanol formed was distilled off.At the end of the reaction, a homogeneous solution was obtained from thetwo phases originally present. Heating was than continued for anadditional 15 minutes under reflux while a slow stream of ammonia waspassed through the hot solution.

When trans esterification had been completed, the reflux condenser wasdisconnected and amidation of the reaction mixture was completed at anammonia pressure of 5 to 9 bar and a temperature of from 110° C. to 135°C. A fine, white crystalline precipitate separated from the initiallyclear solution. In the course of 5 hours, this precipitate grows to forma thick crystalline paste. The reaction is then complete. After releaseof pressure in the autoclave, the white precipitate was suction filteredto remove the glycollic mother liquor and washed three times with coldwater. 115.1 g (0.675 mol) amounting to 82% of the theoretical yield, ofpure cyclohexane-1,4-dicarboxylic acid diamide, having a melting pointof 345° C. to 350° C., was obtained after drying. 14.0 g, amounting to10% of the theoretical yield of cyclohexane-1,4-dicarboxylic aciddiamide were found in the glycollic filtrate and an additional 9.15 g,amounting to 7% of the theoretical yield, in the wash water. The actualyield of diamide is thus 99% of the theoretical yield.

The mother liquor, together with the cyclohexane-1,4-dicarboxylic aciddiamide dissolved in it, was used again for the next batch without anyfurther treatment, i.e. it was reacted with the cis/trans mixture ofcyclohexane-1,4-dicarboxylic acid dimethyl ester. The yield ofcyclohexane-1,4-dicarboxylic acid diamide which was obtained directly byfiltration from the glycollic medium was thus raised to 95-97% of thetheoretical yield.

EXAMPLE 2

By a method similar to that of Example 1, 163.7 g ofcyclohexane-1,4-dicarboxylic acid dimethyl ester (cis/trans ratio=1:1)were mixed with 564 g of ethylene glycol in a 1 liter glass autoclaveand then heated to 80° to 110° C., reacted in the presence of ammonia ascatalyst and finally completely decomposed into thecyclohexane-1,4-dicarboxylic acid diamide by heating to 110° C. to 135°C. under an ammonia pressure of 5 to 9 bar. 119.2 g (0.7 mol) equivalentto 85.5% of the theoretical yield, of cyclohexane-1,4-dicarboxylic aciddiamide could be directly obtained after cooling to room temperature,filtration of the glycollic mother liquor and washing of the residuewith ice water.

EXAMPLE 3

By a method similar to that of Example 1, 163.7 g ofcyclohexane-1,4-dicarboxylic acid dimethyl ester (cis/trans ratio=1:9)were trans esterified with 564 g of ethylene glycol and then decomposedinto cyclohexane-1,4-dicarboxylic acid diamide by heating totemperatures of from 110° C. to 140° C. at an ammonia pressure of 5 to10 bar. 129.0 g (0.758 mol), equivalent to 92.6% of the theoreticalyield of cyclohexane-1,4-dicarboxylic acid diamide were obtained fromthe glycollic reaction mixture after filtration and repeated washingwith water at 15° C. A further 9.0 g=6.47% ofcyclohexane-1,4-dicarboxylic acid diamide were dissolved in theglycollic filtrate and 1.84 g=1.32% were dissolved in water.

EXAMPLE 4

224 g (1.30 mol) of cyclohexane-1,4-dicarboxylic acid (cis/trans mixture7:3) and 1,000 g of ethylene glycol were heated under reflux for 1 hourat 190° C. to 195° C. with stirring in the presence of 0.5% by weight ofantimony trioxide, based on the quantity of cyclohexane-1,4-dicarboxylicacid. 600 g of ethylene glycol/water (about 47 g water of reaction) weresubsequently distilled off at normal pressure over a period of 5 hours.The oily residue, an oligomeric mixture in excess ethylene glycol, wastransferred to the autoclave described in Example 1 and treated withammonia as also described in that Example. The reaction temperature was120° C., the ammonia pressure 9 bar and the reaction time 10 hours. Theautoclave pressure was then released and the contents cooled to roomtemperature. 250 ml of water were added to the reaction suspension whichcontained about 400 g of glycol. The reaction mixture was then filteredand washed, first with 200 ml of water and then with 100 ml of methanol.195 g, equivalent to 87.2% of the theoretical yield, ofcyclohexane-1,4-dicarboxylic acid diamide in the purest form were leftafter drying. A further quantity of cyclohexane-1,4-dicarboxylic aciddiamide amounting to 10% of the theoretical yield, was found to bedissolved in the mother liquor.

EXAMPLE 5

224 g (1.30 mol) of cyclohexane-1,4-dicarboxylic acid (cis/trans=3:2)and 1,500 g (24.2 mol) of ethylene glycol were heated under reflux in a2 liter glass autoclave for 45 minutes with stirring. 750 g ofglycol/water were subsequently distilled off at normal pressure over aperiod of 5 hours. Esterification was by then completed (determinationof acid number) and, when the autoclave contents had cooled to 130° C.,ammonia was introduced at a pressure of 6 bar for 3 hours and thecontents at the same time thoroughly mixed. The autoclave was thencooled and released to normal pressure and the reaction suspension wasfiltered. The filter residue, moist with glycol, was then washed twice,each time with 100 ml portions of methanol or water, respectively, andthen dried under vacuum at 60° C. to 80° C. The yield of purecyclohexane-1,4-dicarboxylic acid diamide was 187 g, equivalent to 83.6%of the theoretical yield.

After removal of the methanol and water, the glycollic filtrate wascirculated together with the wash waters, i.e. it was reacted with freshcyclohexane-1,4-dicarboxylic acid as described above. The yield of solidcyclohexane-1, 4-dicarboxylic acid diamide was thereby increased to 89%of the theoretical yield after the second cycle and to 93.5% of thetheoretical yield after the third cycle.

The following Examples 6 and 7 relate to the chlorination of the diamideto bis-N-chloramide in aqueous or hydrochloric acid suspension.

EXAMPLE 6

172 g (1.01 mol) of cyclohexane-1,4-dicarboxylic acid diamide preparedaccording to one of the Examples 1 to 4 (filter residue) were dispersedin 2 liters of 17% hydrochloric acid at 5° C. with vigorous stirring anda powerful stream of chlorine was then passed through this suspensionfor 30 minutes. The reaction temperature should not exceed 10° C. duringthis operation. The mixture was stirred very vigorously to ensureefficient mass transfer. Chlorination was completed after 90 minutes andthe cyclohexane-1,4-bis-N-chloramide was separated from the suspensionby filtration through a glass frit and washed 3 times with 100 mlportions of cold water (5°-10° C.). The yield was 225 g (0.942 mol)=93%of the theoretical yield. Cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide was obtained in the form of pure white crystals,which were then dried at 40° C. The percentage of active chlorinedetermined by titration was found to be 99.5% of the theoretical amount.

EXAMPLE 7

17.2 g of cyclohexane-1,4-dicarboxylic acid diamide (0.101 mol) preparedaccording to Example 5 (filter residue) were suspended in 130 ml ofwater in a glass autoclave and then reacted under conditions of vigorousstirring for 15 minutes under a chlorine pressure of 5 to 8 bar at 5° to15° C. The pressure was then released and the precipitate filtered offand washed free from chlorine with ice water. 22.0 g (0.092 mol)=91% ofthe theoretical yield of cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide were obtained. The active chlorine contentdetermined by titration was found to be 99.2% of the theoretical amount.

The following Example 8 relates to the preparation oftrans-cyclohexane-1,4-diamine.

EXAMPLE 8

In a 250 ml 3-necked flask, 9.57 g (0.04 mol) ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide were dispersed in 70ml of water with vigorous stirring, and a solution of 10.4 g (0.26 mol)of sodium hydroxide in 100 ml of water was added dropwise at 5° C. Thereaction temperature should not exceed 8° C. When all the sodiumhydroxide solution had been added, a clear solution was obtained(formation of N-chloramide sodium salt). The external cooling means werethen removed and replaced by a water bath at 35° C. When the reactiontemperature reached 27° C., a vigorous exothermic reaction took place sothat the temperature of the reaction mixture rose to 66° C. After afurther 4 minutes, the reaction temperature began to fall. The mixturewas then reheated at 50°-75° C. for 45 minutes. A clear, light brownsolution was finally obtained. This was extracted with chloroform for3.5 hours in a liquid-liquid extractor. 4.273 g (37.42 mMol)=93.5% ofthe theoretical yield of pure trans-cyclohexane-1,4-diamine was obtainedfrom the chloroform phase after dehydration over calcium chloride andremoval of the solvent. The diamine was obtained in the form ofcolorless needles (melting point 53°-60° C.). It was identified byanalysis of the elements, the IR, NMR and mass spectra and by titration(perchloric acid/acetic acid=99.18%).

The following Examples 9 to 12 relate to the preparation oftrans-diurethanes.

EXAMPLE 9

In a 2 liter 3-necked flask equipped with a KPG stirrer, refluxcondenser and dropping funnel, 41.16 g (1.03 mol) of finely powderedsodium hydroxide were first dissolved in 1.2 liters of methanol withvigorous stirring. The reaction temperature rose to 40° C. The contentswere then cooled to 5° C. and 123.0 g (0.5145 mol) ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide (prepared accordingto Example 6) were added portion-wise over a period of 1 hour at such arate that the temperature in the reaction vessel did not rise above 10°C. When all 123.0 g had been added, a clear solution (sodium salt ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide) was obtained. Thecooling bath was then removed and the Hofmann reaction started byheating to 24° C. The temperature inside the flask rose to 45° C. due tothe heat of reaction liberated. Shortly after onset of the Hofmannrearrangement, the clear solution became cloudy due to precipitation ofsodium chloride. Most of the reactant had undergone reaction after 15minutes, as could be detected by a fall in the reaction temperature to35° C.

The mixture was then heated to 45° C. for 90 minutes and finallyrefluxed for 1 hour to complete the reaction. It was then cooled to roomtemperature and the trans-dimethyl-1,4-cyclohexane-dicarbamate wasfiltered off together with the precipitated sodium chloride. The filterresidue was washed free from chloride with water, and 98.8 g (0.43 mol),equivalent to 83.5% of the theoretical yield, of puretrans-dimethyl-1,4-cyclohexane dicarbamate (melting point 265° to 267°C.) remained behind. A further 9.6 g, equivalent to 7.2%, of thetheoretical yield of trans-dimethyl-1,4-cyclohexane dicarbamate werecontained in the methanollic filtrate and the wash water.

EXAMPLE 10

By a method similar to that of Example 9, 16 g (0.4 mol) of finelypowdered sodium hydroxide were dissolved in 250 ml of ethanol withvigorous stirring, and 47.8 g (0.2 mol) of cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide, synthesized according to Example 6 were addedportion-wise at 0°-5° C. The clear solution was then heated to 28° C.,at which point Hofmann rearrangement set in and the reaction temperaturerose to 52° C. After the reaction had died down, the mixture wasvigorously stirred for 1 hour at 60° C. and then under reflux for 15minutes. After cooling to 10° C., the reaction mixture (sodium chlorideand trans-diethyl-1,4-cyclohexane dicarbamate) was separated byfiltration and the urethane was freed from sodium chloride impurities bywashing with water. The yield of pure trans-diethyl-1,4-cyclohexanedicarbamate (melting point 245° to 248° C.) was 48.6 g (0.188 mol),equivalent to 94% of the theoretical yield.

EXAMPLE 11

191.2 g (0.8 mol) of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide(prepared according to Example 6) were added portion-wise to a solutionof 64 g (1.6 mol) of sodium hydroxide in 2 liters of ethylene glycolwith vigorous stirring at 10° C. with external cooling. When all thechloramide had gone into solution, the cooling means were removed andthe reaction mixture was heated to 40° C. Hofmann rearrangement set inand the reaction temperature rose to 62° C. The reaction mixture wasthen heated to 60° C. for 30 minutes to complete the reaction and thenstirred at room temperature for 10 hours. Thetrans-di-(2-hydroxyethyl)-1,4-cyclohexane dicarbamate formed in thereaction, together with sodium chloride adhering to it, was separatedfrom the glycollic mother liquor by filtration. Residues of ethyleneglycol and sodium chloride still adhering to it were then removed bysuspending the reaction product three times in 50 cc portions of icewater. 128.5 g (0.4426 mol), equivalent to 55% of the theoretical yield,of pure trans-di-(2-hydroxyethyl)-1,4-cyclohexane dicarbamate, meltingpoint 197° C. to 199° C., were obtained in this way. A further 98.2 g(0.338 mol), equivalent to 42% of the theoretical amount, oftrans-di-(2-hydroxyethyl)-1,4-cyclohexane dicarbamate were obtained fromthe mother liquor and the wash water by removing all of the solventunder vacuum and separating the diglycol urethane from the sodiumchloride which had been precipitated with it by extraction with coldethanol.

EXAMPLE 12

Similarly to Example 11, 179.5 g (0.75 mol) ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide were addedportion-wise with vigorous stirring to a solution of 60 g (1.5 mol) ofsodium hydroxide in 2 liters of butane-1,4-diol at 10° C. and Hofmannrearrangement was then carried out at 30°-40° C. After a reaction timeof 5 hours, the reaction mixture was no longer oxidizing, and part ofthe trans-di-(4-hydroxybutyl)-1,4-cyclohexane-dicarbamate formed in thereaction had been precipitated together with sodium chloride. Afterfiltration and removal of the adhering sodium chloride by washing withwater, 120 g (0.3465 mol)=46.2% of the theoretical yield of puretrans-di-(4-hydroxybutyl)-1,4-cyclohexane dicarbamate (Mp 170° to 175°C.) were obtained in the form of fine white needles. A further 98.3 g(0.284 mol), equivalent to 37.9% of the theoretical amount, oftrans-1,4-diurethane were obtained from the mother liquor after removalof the solvent and extraction of the residual salt with cold ethanol.

The following Examples 13 to 19 relate to the preparation oftrans-diureas.

EXAMPLE 13

182 g (0.76 mol) of 1,4-cyclohexane-bis-N-chloramide, prepared accordingto Example 6, were suspended in 750 cc of water with vigorous stirring,and 60.8 g (1.52 mol) of sodium hydroxide dissolved in 300 ml of waterwere added dropwise at temperature between 0° to 5° C. 200 ml ofdiethylamine (1.9 mol) were then added drop-wise to the clear solution(sodium salt of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide) overa period of 10 minutes. The reaction mixture was then heated to 40° C.for 60 minutes and then for a further 45 minutes to 55° C. to completethe reaction. A fine sludge oftrans-(1,4-di-(N',N'-diethyl-ureido)-cyclohexane then formed. This wasisolated by filtration through a glass frit and washed 5 times with 250ml portions of water. After drying, 175.7 g (0.562 mol), equivalent to74% of the theoretical yield, of puretrans-1,4-di-(N',N'-diethyl-ureido)-cyclohexane were obtained in theform of colorless needles, melting point 225° C. to 228° C. The filtratewas then neutralized with dilute hydrochloric acid, evaporated todryness and extracted with acetone. A further 54.6 g (0.174 mol),equivalent to 23% of the theoretical yield, of the pure trans-urea werethereby obtained. The total yield of puretrans-1,4-di-(N',N'-diethyl-ureido)-cyclohexane was therefore 97% of thetheoretical yield.

EXAMPLE 14

47.9 g (0.2 mol) of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide(obtained according to Example 6) were added portion-wise to 500 ml ofconcentrated ammonia at 0° C. with vigorous stirring, care being takento insure that the reaction temperature did not exceed 5° C. A clearsolution formed shortly after all the chloramide had been introducedinto the reaction solution. The cooling bath was then removed and thereaction mixture heated to 30° to 35° C. A fine crystalline precipitatesoon began to form. The reaction mixture was stirred for a further 3hours at 40° C. to complete the reaction. The mixture was then no longeroxidizing. The trans-1,4-diureido-cyclohexane formed in the reaction wasisolated by filtration. It was washed twice, each time with 75 ml of icewater, to remove ammonium chloride adhering to it as impurity. Afterdrying, 34.8 g (0.174 mol), equivalent to 87% of the theoretical yield,of trans-1,4-diureido-cyclohexane (Mp>320° C.) were obtained in the formof colorless needles. An additional portion of the urea was stillpresent in the ammoniacal filtrate, from which it could be recovered byextraction with ethyl acetate after evaporation of the water.

EXAMPLE 15

Similarly to Example 13, 182 g (0.76 mol) ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide were suspended in 700ml of water with vigorous stirring, and 60 g (1.5 mol) of sodiumhydroxide dissolved in 250 ml of water were added drop-wise at 0°-5° C.After a clear solution had formed and cooled to 0° C., 128 g (2.1 mol)of ethanolamine were added. The temperature should not exceed 5° C.throughout the addition of ethanolamine. The clear solution was thenheated to room temperature, at which point Hofmann rarrangement set inand a fine white precipitate formed at 33° C. The reaction mixture wasthen vigorously stirred for one hour at 50° C. to complete the reaction,and the urea formed was isolated by filtration and freed from the sodiumchloride adhering to it by washing with ice water. 177.5 g (0.616 mol),equivalent to 81% of the theoretical yield, oftrans-1,4-di-(N'-2-hydroxyethyl ureido)-cyclohexane could be obtainedafter drying.

EXAMPLE 16

47.9 g (0.2 mol) of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide,prepared according to Example 7, were vigorously stirred up in 250 ml ofwater to form a fine suspension, and 16 g (0.4 mol) of sodium hydroxidedissolved in 75 ml of water were added at 0° C. 43.56 g (0.5 mol) ofmorpholine were added dropwise to this solution. Hofmann rearrangementand working up of the reaction product were carried out analogously toExample 1. 46.25 g (0.136 mol), equivalent to 67.9% of the theoreticalyield, of pure trans-cyclohexane-1,4-bis-morpholine-urea were obtainedfrom the reaction mixture in the form of a white powder (Mp>320° C.) byfiltration. A further 12.8 g equivalent to 19% of the theoretical yieldof the urea were isolated from the mother liquor by extraction withethyl acetate after evaporation.

EXAMPLE 17

Similarly to Example 13, 24 g (0.1 mol) of cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide (synthesized according to Example 6) weresuspended in 100 ml of water at 0° C., and 8.4 g (0.21 mol) of sodiumhydroxide dissolved in 25 ml of water were added. When salt formationhad been completed, 20 g of cyclohexylamine (0.2016 mol) were added withfurther cooling and the Hofmann rearrangement was then carried out. 26.7g (0.073 mol), equivalent to 73% of the theoretical yield, of puretrans-1,4-di-(N'-cyclohexylureido)-cyclohexane were obtained byfiltration. This substance precipitates in the form of white needleswhich begin to decompose slowly at 300° C.

EXAMPLE 18

Similarly to Example 13, 119.6 g (0.5 mol) ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide (prepared accordingto Example 7) were dispersed in 750 ml of water at 0° C., and 46 g ofsodium hydroxide (1.15 mol) dissolved in 120 ml of water were addeddropwise. 80 g of tertiary butylamine (1.1 mol) were subsequently added.Hofmann rearrangement and isolation of the urea were carried outsimilarly to Examples 13 to 17. The yield of puretrans-1,4-di-(N'-tertiary butyl-ureido)-cyclohexane (colorless crystals,decomposition point >300° C.) was 118 g (0.3776 mol), equivalent to 75%of the theoretical yield.

EXAMPLE 19

Similarly to Example 13, 36 g (0.9 mol) of sodium hydroxide dissolved in250 ml of water were added at a low temperature to 100 g (0.418 mol) ofcyclohexane-1,4-dicarboxylic acid-bis-N-chloramide, prepared accordingto Example 6, and, when salt formation had been completed, 200 g (1.04mol) of N,N'-diisopropyl-p-phenylene diamine were added. Hofmannrearrangement and separation of the urea formed in the reaction werecarried out as described in Examples 12 to 17. 187 g (y0.34 mol),equivalent to 81% of the theoretical yield, of puretrans-1,4-di-(N'-isobutyl-N'-p-isobutylaminophenyl-ureido)-cyclohexanewere obtained by filtration as a beige colored powder having adecomposition point at 245° to 247° C.

The following Example relates to the preparation of atrans-cyclohexane-1,4-disulphonyl urea.

EXAMPLE 20

32 g (0.80 mol) of sodium hydroxide were dissolved in 40 g of water. 400ml of dimethyl formamide were added at 25° C. 68.5 g (0.40 mol) offinely powdered p-toluene sulphonamide were added portion-wise to thissolution at room temperature with vigorous stirring. The sodium salt ofthe tosylamide was thereby formed, which precipitated as fine, whitecrystals. The suspension was then cooled to 5° C. and a slurry of 47.6 g(0.20 mol) of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide in 100ml of dimethyl formamide was added with vigorous stirring. The heat ofreaction (formation of the sodium salt of bis-N-chloramide) was removedby cooling (reaction temperature >15° C.). When all the N-chloramide hadbeen introduced into the reaction mixture, the mixture was heated to 25°C. An exothermic reaction then took place and the reaction temperaturerose to 48° C. The suspension was highly fluid, and a white precipitatewas formed after about 5 minutes. The reaction mixture was heated to 50°C. for 55 minutes to complete the reaction. It was then diluted with 1liter of water and freed from undissolved constituents. The filtrate wasthen acidified to pH=2 with dilute mineral acid. A colorless, bulkyprecipitate formed, which was dried in a vacuum drying oven at 80° C.after it had been washed free from chlorine. The yield oftrans-1,4-cyclohexyl-bis-(p-tolyl-sulphonyl urea) was 64.2 g (0.25 mol),equivalent to 62.4% of the theoretical yield. (Mp >350° C.).

Examples 21 to 25 relate to the preparation oftrans-cyclohexane-1,4-diisocyanate.

EXAMPLE 21

19.16 g (0.08 mol) of cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide(synthesized as in Example 7) were finely divided in 75 ml of water at0° C. with vigorous stirring. 6.4 g (1.16 mol) of sodium hydroxidedissolved in 75 ml of water were then added dropwise at such a rate thatthe temperature in the reaction vessel did not rise above 5° C. A clearsolution formed when all of the sodium hydroxide had been added. 20 g(0.177 mol) of a 40% by weight aqueous dimethylamine solution was addeddropwise with cooling and the reaction mixture was then heated. Thesolution became cloudy at 25° C. and the temperature of the reactionmixture rose to 46° C. and at the same time the quantity of precipitateincreased. The reaction mixture was stirred for 2 hours at 50° C. tocomplete the reaction. At the end of that time, it was no longeroxidizing. The alkaline solution was then adjusted to pH 6 with dilutehydrochloric acid and the whole suspension was then pumped through atube into 250 ml of o-dichlorobenzene which had been heated to 110° C.The water distilled off at the top and a beige colored, salt like massprecipitated in the o-dichlorobenzene. Finally, 30 ml ofo-dichlorobenzene were distilled off under vacuum at 110° C. to removethe last traces of water. The suspension of substituted urea, sodiumchloride and dimethylamine hydrochloride left behind was heated to 150°C. to 155° C. and saturated with HCl gas in the course of 30 minutes. Itwas then cooled to 100° to 110° C. and the hydrogen chloride dissolvedin it was removed by careful stripping with a stream of nitrogen over aperiod of 1 hour. The residue was then cooled to 10° C. and thediisocyanate formed was filtered from sodium chloride and dimethylaminehydrochloride. The filter residue was washed 3 times with 25 ml portionsof o-dichlorobenzene and the combine filtrates were fractionallydistilled. 10.67 g (0.064 mol), equivalent to 80% of the theoreticalyield, of pure trans-cyclohexane- 1,4-diisocyanate (Mp 62° to 64° C.),distilled over at 117° C. to 120° C./10 to 13 torr.

EXAMPLE 22

In a 1 liter glass autoclave, 161 g (0.517 mol) oftrans-1,4-di-(N',N'-diethylureido)-cyclohexane (prepared as in Example13) were suspended in 700 ml of chlorobenzene and heated to 150° C. HClgas was then forced in at a pressure of 6 bar with vigorous stirring.After 45 minutes, the autoclave was cooled to 80° C. to 100° C. and thepressure released.. Most of the diethylamine hydrochloride produced inthe reaction was obtained in the form of colorless, shiny platelets. Thereaction mixture was carefully stripped with an inert gas (nitrogen,carbon dioxide) for an additional 30 minutes to remove any dissolved HClgas and decompose any carbamoyl chloride formed, and the mixture wasthen cooled to 10° C. and filtered to remove diethylamine hydrochloride.The filter residue was washed twice with 250 ml portions ofchlorobenzene. 77.3 g (0.465 mol), equivalent to 90% of the theoreticalyield, of pure trans-cyclohexane-1,4-diisocyanate (Mp 63° to 64° C.)precipitated in the for of colorless scales from the combinedchlorobenzene filtrates after fractional distillation.

EXAMPLE 23

A mixture of 50 g (0.218 mol) of trans-dimethyl-1,4-cyclohexanedicarbamate (synthesized according to Example 9) was heated to 220° C.in 300 ml of n-hexadecane and kept at this temperature for 3 hours. Atthe same time, a stream of nitrogen was passed through the reactionmixture at the rate of 15 liters per hour. The methanol formed in thereaction distilled off at the top of a condenser which was maintained at80° C. After the reaction had been completed, the reaction mixture wascooled to 10° C. and filtered to remove unreacted diurethane,monoisocyanate and a certain quantity of polymeric constituents. 63.7%of trans-cyclohexane-1,4-diisocyanate (MP 60°-63° C.) were obtained fromthe filtrate. EXAMPLE 24

48.5 g (0.188 mol) of trans-diethyl-1,4-cyclohexane-dicarbamate(synthesized according to Example 10) were heated to 420° C. in anevaporator and passed over a 25 meter long bed of Raschig rings(temperature 450° C.) together with a stream of nitrogen (25 liters perhour), and the vapors liberated were rapidly chilled to 100° C.Trans-cyclohexane-1,4-diisocyanate (52.2% of the theoretical yield)formed in the process was separated from ethanol (89.7% of thetheoretical amount) by fractional condensation before those twocomponents could recombine to form the urethane.

EXAMPLE 25

64.2 g (0.25 mol) of trans-1,4-cyclohexane-bis-(p-tolyl-sulphonyl-urea)prepared as in Example 20 were reacted in 350 ml of nitrobenzene in a 1liter glass autoclave at 230°-250° C. for 2 hours with stirring. Thepressure was then released from the resulting clear solution and thenitrobenzene used as solvent was distilled off under vacuum. 20.7 g(0.124 mol), equivalent to 49.7% of the theoretical yield, of puretrans-1,4-cyclohexane diisocyanate were obtained from the solid,salt-like residue by extraction with hot hexane. The residue consistedof a mixture of p-toluene sulphonamide, the sulphonyl urea originallyput into the process, monoisocyanate and polymeric acyl urea.

Although the invention has been described in detail for the purpose ofillustration, it is to be understood that such detail is solely for thatpurpose and that variations can be made therein by those skilled in theart without departing from the spirit and scope of the invention exceptas it may be limited by the claims.

What is claimed is:
 1. A process for preparing atrans-cyclohexane-1,4-diisocyanate which comprises (a) reacting ammoniawith cyclohexane-1,4-dicarboxylic acid, or a lower alkyl ester, a glycolester, an oligomeric ester or a polyester thereof or a mixture of suchcompounds at an ammonia partial pressure of from 0.1 to 50 bar in apolyhydric alcohol at a temperature of from about 25° C. to about 200°C., (b) separating the resulting solid dicarboxylic acid diamideprecipitated under these conditions from the reaction mixture, (c)freeing the solid diamide from water soluble constituents adheringthereto, (d) suspending the resulting solid diamide in an aqueousmineral acid or in water, (e) chlorinating the diamide at a temperatureof from 0° C. to 40° C. to form cyclohexane-1,4-dicarboxylicacid-bis-N-chloramide, (f) reacting the chloramide with a monohydricalcohol, a polyhydric alcohol, or a carbocyclic or heterocyclic phenolwhich is capable of at least partly dissolving an alkali metal oralkaline earth metal hydroxide in the presence of said alkali metal oralkaline earth metal hydroxide to form trans-cyclohexane-1,4-diurethane,and (g) heating said trans-cyclohexane-1,4-diurethane to formtrans-cyclohexane-1,4-diisocyanate.